If your blog supports UTF-8 encoding then it is very easy to write and comment in Malayalam in your blog. This method should also be applicable for any of your sites that support UTF-8. Your website should support storage of UTF-8 characters in your application's database and also you should have a
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
in your pages where you want to read or write Malayalam

This is a modification on the tool Varamozhi Offline that allows you to save an html page on to your system and use that to type in Malayalam. The original code for Varamozhi Offline is from Alex benenson's cyrillic translitarator.

Add the following lines of code in the page where you have the textarea or input box where you want to type in Malayalam.

<script type="text/javascript">
textControlID = "yourTextControlName";
</script>
<script type="text/javascript" src="http://www.zyxware.com/freeware/mozhi_script/mozhi_script.js">
</script>

Make sure that you replace yourTextControlName with the name of the text control where you want to type in Malayalam.

The original code has only been slightly modified to enable inclusion in any page. We are planning to add some more features like conversion of selected text, realtime display of text being typed etc. Do check back for more updates.